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DIAPHRAGM FOB SOUN'JIBOZES.

1,33,@fi(9. il'o Drawing.

To all whom it may concern: I

Be it known that I, DONATI l): CARLO, a

subject of the King of Italy, having declared myintention ofbecoming a citizen of the United States, and a resident of Philagu mtrohydrocarbon, or suitable solvent macounty of Philadelphia, State or have invented Diaphragms of which the following is delphia, Pennsylvania, for Sound-Boxes, a specification. I

My invention relates to diaphragms' for use in. oonnect'on with sound reproducing instruments, as, for instance, in the sound box of a talking machine; the object of my invention being the formation of a diaphragm combining improved sound transmitting qualities with strength and dura bility and with an extremely low production cost.

In general, the diaphragm consists of a base of mineral material possessing the characteristics of cement, such as china clay orplaster of Paris, to which is addedan amount of. a

metallic oxi-d or oxids, preferably oxid of zinc, these materials being incorporated with a mucilaginous binder such asshellac or glue. In forming the diaphragm I have obtained the best results by subjecting the mixture to heat until the mass is thoroughly after which it is poured into molds of the desired shape and size and al lowed to cool and to set. This diaphragm I disk I have found to possess greatly 1mproved sound transmitting qualities, is

' strong and durable, and the cost of-the raw total volume of the mass.

materials and of production are very low. As a specific example of my invention, I may form a mixture of plaster ofParis, oxid oil zinc, and White glue, and Water, these substances forming approximately 50%, 1W7) and 10% respectively of the lent is now applied to this mixture until the glue is dissolved and the mass thoroughly incorpo' rated, after which it is and allowed to. cool. The addition or: a small amount oi lamp blackivill make the material him-l: it this is desired, Without otherwise arise-ting the finished moduct.

Specification of Letters'Patent.

binder.

poured into molds Patented Feb. ill 123% Application filed February 26, 1919. Serial No. 279,391.

As previously stated," various metallic oxids may be employed, though I believe the oxid of zincgives the best results, and this -oxid is therefore preferred. When m shellac" is employed as the binder, a

terial for the shellac, must also be used,

such solvent material not acting to alter thecharacteristics of the finished diaphragm. Lamp black may beemployed to-blacken the diaphragm material if desired.

stood that I do not wish to be limited to any set formula, nor to any fixed method of forming the diaphragm. But what I claim" as my invention and desire protection upon 1s:

apparatus comprising a cementitious mineral base, a metallic mud, and a mucilaginous binder.

2.-A diaphragm. for sound reproducing 1. A diaphragm for sound reproducing apparatus comprisinga base of plaster of Paris, a metalhc oxid, and a mucilaginous 3. A diaphragm for -sound reproducing apparatus comprising a base ofplaster of Paris, oxid of. zinc, and a mucila-ginous binden- "4. A diaphragm for sound reproducing apparatus comprising plaster-of Paris. oxid of zinc, and glue, the ratio of the volumes of such comprised substances being approximately to 10 to'30 respectively.

5, The process of forming a diaphragm for sound reproducing apparatus comprising intimately mixin 50 parts by volume of plasterof Paris with 10 parts of oxid of zinc and 30 parts of glue, adding approxi mately 1Q parts of water, applying heat to said mixture until the glue is dissolved and t e mass thoroughly incorporated, and pouring said incorporated mixture into molds and allowing it to cool therein.

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